1. Field of the Disclosure
The present disclosure relates generally to electrophotographic imaging devices such as a printer or multifunction device having printing capability, and in particular, to a cleaner unit assembly used for cleaning a photoconductive drum.
2. Description of the Related Art
Image forming devices such as copiers, laser printers, facsimile machines, and the like, include a photoconductive drum having a rigid cylindrical surface that is coated along a defined length of its outer surface. The surface of the photoconductive drum is charged to a uniform electrical potential and then selectively exposed to light in a pattern corresponding to an original image. Those areas of the photoconductive surface exposed to light are electrically discharged thereby forming a latent electrostatic image on the photoconductive surface. A charged developer material, such as toner, is brought into contact with the photoconductive drum's surface by a developer roller such that the charged toner attaches to the discharged areas of the photoconductive surface. The toner on the photoconductive drum is then transferred onto a recording medium, such as a media sheet or a transfer belt for subsequent transfer to a media sheet.
During transfer of the toner to the recording medium, some of the toner may not be transferred and may remain on the photoconductive drum. If not removed, such residual toner may contaminate the charge roll or inadvertently transfer to a subsequent media sheet resulting in print defects. Accordingly, removal of the residual toner is necessary prior to preparing the photoconductive drum to receive a new image in order to prevent or reduce the likelihood of print defects.
In preparation for a next imaging forming cycle, the photoconductive surface may be optionally discharged and cleaned by a cleaner blade. The cleaner blade may be positioned in proximity to the photoconductive drum such that its edge contacts the photoconductive surface to wipe off residual toner therefrom. However, the cleaner blade pressed against the photoconductive drum may become damaged when operated under low lubrication. Toner acts as a lubricant which prevents friction at the cleaner blade edge from getting too high. If there is no lubrication at the cleaner blade edge, the frictional forces acting on the cleaner blade may cause the cleaner blade to flip.
The cleaner blade may extend well across the entire length of the photoconductive drum including an imaging region at a central portion and the non-imaging regions at end portions thereof. Since the non-imaging end regions of the photoconductive drum typically receive little or no toner, the end sections of the cleaner blade are more prone to low lubrication. In addition, the end sections of the cleaner blade lack stiffness relative to central portions thereof and end seals that prevent leaks at the ends of the cleaner blade press against the back side of the cleaner blade which increases the frictional force at the cleaner blade ends. As a result, cleaner blade flip typically starts at the cleaner blade ends and progresses across the full length of the cleaner blade.
Some approaches to solving cleaner blade flip problems include minimizing the length of the blade, applying lubricants to the cleaning blade itself or the photoconductive drum surface, modifying blade end sealing designs, and reducing forces applied at the ends of the cleaner blade by modifying blade support bracket designs. These methods, however, may have drawbacks in terms of cost and reliability. For example, minimizing blade width requires tight tolerances of the cleaner unit assembly which may still result in at least some level of blade end lubrication problems. Meanwhile, lubricants are typically not reliable as they are removed over the course of operation and can be subject to assembly variation when applied by human operators. End sealing design modifications, on the other hand, can act to reduce blade end forces but come at the cost of a compromise to sealing performance. Furthermore, modifying cleaner blade bracket designs to vary a load gradient across the cleaner blade adds cost and complexity to the cleaner unit assembly.
Based upon the foregoing, there is a need for a simple and a low cost solution for preventing cleaner blade failures.